Abstract PS01-06: The relationship between margin status of 2mm and local recurrence in DCIS patients

Abstract Background: There has been controversial evidence regarding adequate margin in breast conserving surgery (BCS) for ductal carcinoma in situ (DCIS). However, the consensus is a surgical margin distance of 2 mm. Moreover, recent recommendations advised on ‘’clinical judgement’’ approach to re-excision in cases of margin distance 2mm. The ongoing controversy in DCIS margin compared to invasive cancer margin is due to the differences in post operative management. This is important as margin status is one of the modifiable risk factor for local regional recurrence in DCIS. In our study we evaluated margin distance in patient diagnosed with DCIS who underwent BCS on local recurrence Methods: Patients who underwent breast conserving surgery between February 2000 and December 2018 at Asan Medical Center were retrospectively reviewed. Patients with involved resection margins were excluded. Kaplan-Meier survival analysis and Cox proportional hazard models were applied to determine the relationship between negative margin width and local recurrence. Results: A total of 1,858 patients were included in the study. Almost half of the patients had a tumor size of 1cm or smaller (n=876, 47.1%). Only 98 (5.3%) patients did not undergo radiation therapy. A negative margin width of 1mm, 2mm, 5mm were all not associated with local recurrence (log-rank test p-value 0.1, 0.1, 0.078, respectively). For patients who underwent radiation therapy, a negative margin of any width was not related to local recurrence. Whereas, for patients who did not undergo radiation therapy, those with margins ≤2mm were significantly more likely to develop local recurrence than those with margins 2mm (10-yr local recurrence rate, 16.4% vs 5.5%, respectively; hazard ratio, 5.709; 95% CI, 1.106-29.46, p=0.038). Conclusion: A negative margin is not related to local recurrence in DCIS patients who undergo breast conserving surgery with radiation therapy. Routine additional surgery for wider negative margin may only be needed for patients who do not undergo radiation therapy. Citation Format: Sarah Al Safi, Tae-Kyung Yoo, Sae Byul Lee, Jisun Kim, Il-Yong Chung, Hee Jeong Kim, Beom Seok Ko, Jong Won Lee, Byung Ho Son, Hee Jin Lee, Gyungyub Gong. The relationship between margin status of 2mm and local recurrence in DCIS patients abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS01-06.